This invention relates in general to the measurement of mass streams of fine-grained dusty solid fuels conveyed pneumatically to a gasification reactor or burner.
Known are methods and arrangements for determining the mass stream for dusty and fine-grained materials which either transmit qualitative measuring signals without indication of exact quantitative measuring values or which are suitable for pneumatic transportation of mass streams having an extremely low density of solid particles (.rho..sub.f2 less than 30 kg/m.sup.3).
From DD Pat. Nos. 199 246 and 145 958 measuring methods of the above described are known which deliver analog values of the mass streams. Such analog signals can be employed for an exactly defined density condition and are reproducible for a definite quality of the dusty fuel and possess sufficient accuracy for technical applications. These analog methods, however, require recalibration when the quality of conveyed dust fuel changes. From DD Pat. No. 142 606 an optical measuring process is known which has the capacity of simultaneously producing multiple measuring values. Nevertheless, due to the lack of transparency and light-reflecting qualities of coal dust, this prior-art method is not suitable in two-phase mass streams. From German Pat. Nos. 2,554,565, 2,902,911 and 2,757,032, measuring methods are known which result in only approximate measuring values because they do not consider the actual condition of the dust-gas mixture flowing in the measuring path. Consequently, these methods are inapplicable for streams with high loads of solid particles (.rho..sub.f2 larger than or equal to 50 kilograms per cubic meter).